RESEARCH ARTICLE Open Access

Initiation of and long-term adherence tosecondary preventive drugs after acutemyocardial infarctionSigrun Halvorsen1*, Jarle Jortveit2, Pål Hasvold3, Marcus Thuresson4 and Erik Øie5

Abstract

Background: Secondary preventive drug therapy following acute myocardial infarction (AMI) is recommended toreduce the risk of new cardiovascular events. The aim of this nationwide cohort study was to examine the initiationand long-term use of secondary preventive drugs after AMI.

Methods: The prescription of drugs in 42,707 patients < 85 years discharged alive from hospital after AMI in2009–2013 was retrieved by linkage of the Norwegian Patient Register, the Norwegian Prescription Database,and the Norwegian Cause of Death Registry. Patients were followed for up to 24 months.

Results: The majority of patients were discharged on single or dual antiplatelet therapy (91 %), statins (90 %),beta-blockers (82 %), and angiotensin-converting enzyme inhibitors (ACEI)/angiotensin receptor II blockers(ARB) (60 %). Patients not undergoing percutaneous coronary intervention (PCI) (42 %) were less likely to beprescribed secondary preventive drugs compared with patients undergoing PCI. This was particular the case fordual antiplatelet therapy (43 % vs. 87 %). The adherence to prescribed drugs was high: 12 months after indexAMI, 84 % of patients were still on aspirin, 84 % on statins, 77 % on beta-blockers and 57 % on ACEI/ARB. Fewdrug and dose adjustments were made during follow-up.

Conclusion: Guideline-recommended secondary preventive drugs were prescribed to most patients discharged fromhospital after AMI, but the percentage receiving such therapy was significantly lower in non-PCI patients. The long-timeadherence was high, but few drug adjustments were performed during follow-up. More attention is needed to secondarypreventive drug therapy in AMI patients not undergoing PCI.

Keywords: Acute myocardial infarction, Secondary prevention, Medication adherence

BackgroundIschemic heart disease is a common cause of death in in-dustrialized countries and accounts for a large proportionof hospital admissions in Norway [1]. Approximately13,000 men and women are diagnosed annually with acutemyocardial infarction (AMI) [2]. Secondary preventivedrug therapy, e.g. platelet inhibitors, statins, beta-blockersand angiotensin-converting enzyme inhibitors (ACEI)/angiotensin receptor II blockers (ARB), is recommendedfollowing AMI to reduce the risk of new cardiovascularevents and death [3–7]. However, an underuse of

secondary preventive drugs has previously been observedfollowing AMI, especially in patients not undergoing per-cutaneous coronary intervention (PCI) [8]. Despite theirelevated cardiovascular risk [9], still many AMI patientsare not treated according to guidelines [10]. This may berelated to under-prescription, reduced adherence, and/orunder-dosing of secondary preventive drug therapy[11, 12]. A potential source for the underuse of recom-mended secondary preventive drugs could be the shiftof treatment responsibility from the hospitals to thegeneral practitioners in the primary care setting. Theextent to which the hospital-initiated treatment iscontinued as initially prescribed, the doses adjusted ordrugs switched to another type of drug within thesame drug class, is not known. Comprehensive analyses of

* Correspondence: sigrun.h@online.no1Department of Cardiology, Oslo University Hospital Ulleval and University ofOslo, Postboks 4956, Nydalen 0424, Oslo, NorwayFull list of author information is available at the end of the article

© 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Halvorsen et al. BMC Cardiovascular Disorders (2016) 16:115 DOI 10.1186/s12872-016-0283-6

initiation and adherence in different patient populationsare essential to improve long-term use of secondary pre-ventive drugs and cardiovascular outcomes [13].The aim of this nationwide cohort study was to examine

the initiation and long-term use of secondary preventivedrug in patients hospitalized with AMI in Norway duringthe years 2009 to 2013.

MethodsData sourcesThis observational, historical cohort study was basedon data from three Norwegian national registries: 1)The Norwegian Patient Register covering all hospitaladmissions and including diagnoses according to theInternational Classification of Diseases, 10th revision,Clinical Modification (ICD-10-CM) [14]; 2) the Nor-wegian Prescription Database registering all pharmacydispenses [15]; and 3) the Norwegian Cause of DeathRegistry registering all deaths [16]. The prescription ofdrugs in patients discharged alive from hospital afterAMI in 2009–2013 was retrieved by linkage of theNorwegian Patient Register, the Norwegian Prescrip-tion Database, and the Norwegian Cause of DeathRegistry. Patients were followed for up to 24 months.The Norwegian Institute of Public Health performedthe data linkage. Data were anonymised before furtheranalysis. The linked database was managed by TheNorwegian University of Science and Technology,Trondheim, Norway.

Study populationAll patients below 85 years of age who were admitted tohospital with a primary diagnosis of AMI (index AMI)(ICD-10: I21) between 1 January 2009 and 30 November2013 and alive 30 days after discharge were included inthis study. Patients 85 years or older were excluded fortwo reasons: 1) their likelihood of long-term use ofsecondary preventive drugs might be extensively con-founded by fragility; 2) older patients have an in-creased risk of long-term institutional stays where thedrug use cannot be captured by the available registries.Patients were classified as PCI and non-PCI patientsdepending on whether PCI was performed or not up to 30days after index-AMI. The study population was furtherstratified into two groups; ≤75 years and 76–84 years.Index AMI was defined as the first recorded primary

diagnosis of AMI for a patient during the specifiedtime-period (not necessarily the patient’s first AMI).All residents in Norway are covered by a nationalhealth security system with a universal tax-funded ac-cess to primary and secondary health care, includingsecondary preventive drugs recommended after AMI.

Follow-upObservational data on drug prescriptions were collectedup to 24 months following AMI, or until 31 December2014 or death (whichever occurred first).

Drug treatment and adherenceDrug treatment at discharge for index AMI were calcu-lated from dispensed drugs from pharmacies one yearwithin and until 30 days after the index AMI; either aprior dispensing covering day 0 to day 30 or a new dis-pensing within day 0 to day 30. Drug adherence was de-fined as the proportion of patients on the treatment ofinterest at each day from 12 months prior to the date ofhospitalization for AMI until a maximum of 24 monthsafter. The calculation of drug use (days on treatment)was based on the prescribed dose and on the number ofpills collected or delivered from the pharmacies. Whetheror not the pills were taken by the patients, were notassessed. If a patient had a gap in collection of drugs, thepatient was defined as a non-user from last calculated daywith available drug. Furthermore, if a patient after a gap,again collected the same drug from the pharmacy, thepatient was defined as a user from that actual date, and ifa patient was switched to another type of drug within thesame drug class after the index AMI episode, the patientwas defined as a user.In the separate analysis of the adherence to the P2Y12-

antagonists clopidogrel, prasugrel or ticagrelor duringthe first 18 months after AMI, the proportion of all pa-tients still alive continuing on the same P2Y12 antagonistas at discharge was estimated.In order to describe changes in drug treatment over

time, treatment at discharge for index AMI was com-pared to treatment in the post AMI period (dispensedduring 12 18 months after the AMI).

Statistical analysesData are presented as mean with standard deviation forcontinuous variables and absolute and relative frequenciesfor categorical variables. Patients were stratified by age(≤75 years or 75–84 years) and by PCI status (PCI or noPCI). Statistical analyses were performed using SAS ver-sion 9.3 (SAS Institute Inc, Cary, NC, USA) and R version3.2.2 [17].

ResultsA total of 57,106 individuals were admitted to Norwegianhospitals for AMI during the study period, of whom45,838 (80.3 %) were younger than 85 years. Of these,42,707 (93.2 %) were alive 30 days after hospital dischargeand could be included in the study (Fig. 1). Overall, 70 %of the patients were men and mean age was 65.8 years(standard deviation 11.8) (Table 1). A total of 58 % of thepatients underwent PCI, with an increasing proportion

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during the study period (from 53 % to 63 %) (Additionalfile 1, Table 1). Patients undergoing PCI were younger andmore often male compared with the medically treatedpatients (Table 1).

Initiation of secondary preventive drugsThe prescription of secondary preventive drugs at dischargeis shown in Tables 1 and 2. The majority of patients weredischarged on single or dual antiplatelet therapy (DAPT)(19 % and 72 %, respectively), statins (90 %), beta-blockers(82 %), and ACEI/ARB (60 %). The percentage receivingthese drugs were slightly lower in patients 75–84 yearscompared to patients ≤75 years, except for ACEI/ARBwhich was prescribed slightly more often in the elderly(Table 1).Patients undergoing PCI were prescribed secondary

preventive drug therapy more often than patients notundergoing PCI (Table 1). This was the case both for pa-tients <75 years and patients 75–84 years. The differencein prescriptions was largest with respect to DAPT, whichwas prescribed in 92 % of the PCI patients vs. 45 % ofpatients not undergoing PCI (Table 1, Figs. 2 and 3). In

contrast, non-PCI patients were prescribed other kindsof antithrombotic therapy more often than PCI patients:Aspirin monotherapy in 28 % vs. 2 %, oral anticoagulant(OAC) monotherapy in 4 % vs. 0 %, or OAC in combin-ation with single antiplatelet therapy in 6 % vs. 1 %, re-spectively. However, 14 % of the non-PCI patients weredischarged with neither antiplatelet drugs nor OAC,compared to 2 % of the PCI patients. Surprisingly, thedifferences in prescription pattern between PCI andnon-PCI patients were found also with respect to othertypes of secondary preventive drugs (Table 1).The mean dose of statins at discharge was 37 mg for

simvastatin (55 % of patients) and 57 mg for atorvastatin(40 % of patients). The mean doses of ACEI/ARB andbeta-blocker at discharge were 35-60 % and 30-50 % ofmaximal recommended doses, respectively (Table 2).

Adherence to secondary preventive drugsThe overall long-time adherence was high among all pa-tients initiated on treatment with statins, beta-blockersand ACEI/ARB (Figs. 2 and 3, Table 2). The proportionsof patients using statins, ACEI/ARB and beta-blockers

Fig. 1 Flow chart of the study population

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were reduced by 6 %, 3 % and 4 %, respectively, afterone year. No major differences in drug adherence wasobserved between PCI and non-PCI patients, or betweenpatients ≤75 and 76–84 years. When primary health carephysicians took over the prescription responsibility forthese patients (approximately 3 months after the AMI),no overall change in adherence was found. Approxi-mately 20 % of patients changed to another drug withinthe same drug class, or changed the dose of statin, beta-blocker and ACEI/ARB within 12–18 months after theAMI (Table 2).The adherence to antiplatelet drugs was also high (Figs. 2

and 3). After 12 months, 84 % of patients were still on as-pirin; 83 % after 18 months. The adherence to P2Y12 in-hibitors are shown in more detail in Fig. 4 and Additionalfile 1: Table S2. Patients not undergoing PCI had a shorterlength of time on treatment with a P2Y12 inhibitor com-pared with PCI patients, with a substantial proportion ofthese patients discontinuing treatment already after threemonths. The majority of the PCI patients treated withticagrelor and prasugrel maintained the treatment through12 months. Many PCI patients on clopidogrel discontin-ued P2Y12 inhibitor after nine months.

DiscussionThis nationwide observational cohort study, includingall patients younger than 85 years surviving an AMI in

Norway during the years 2009 to 2013, showed a generallyhigh long-term adherence to the prescribed treatmentwith antiplatelet drugs, statins, beta-blockers and ACEI/ARB. The shift of responsibility for prescribing secondarypreventive drugs from hospital to primary health careshowed a sustained high use of the originally prescribeddrugs. Only few patients switched to another type of statinor changed the dose of statin, beta-blocker and ACEI/ARB during the first two years after the AMI. For patientsnot undergoing PCI, a smaller proportion was dischargedwith secondary preventive drugs following their AMIcompared with patients undergoing PCI, and less thanhalf were prescribed DAPT at discharge.Contemporary national level data describing long-

term adherence to secondary preventive medications,i.e. antiplatelet drugs, statins, beta-blockers, and ACEI/ARB in AMI populations comparing younger vs. olderand PCI vs. non-PCI patients are scarce. Furthermore,little is known on the impact of change in drug treat-ment responsibilities as AMI patients are transferredfrom hospital care to primary health care.The initiation of secondary preventive drugs in our

study was considerably higher than was found in aprevious Danish nationwide study [12]. In patients ad-mitted with a first AMI between 1995 and 2002 inDenmark, only 58 % received beta-blockers, 29 %ACE-inhibitors, and 34 % statins at discharge [12].

Table 1 Drug treatment at discharge after index AMI. Patients stratified by age (≤75 years or 75–84 years) and by PCI status (PCI orno PCI)

Age ≤75 years Age 75–84 years Total

n = 30 843 n = 11 864 n = 42 707

PCI No PCI PCI No PCI

n = 19 835 n = 11 008 n = 4918 n = 6946

(64.3) (35.7) (29.3) (70.7)

Women 4065 (20.5) 3478 (31.6) 1819 (37.0) 3357 (48.3) 12 719 (29.8)

Age, mean (SD) 59.8 (9.1) 61.6 (9.6) 79.0 (2.8) 80.0 (2.8) 65.8 (11.8)

DAPT 17 505 (88.3) 5107 (46.4) 3877 (78.8) 2597 (37.4) 29 086 (68.1)

Only P2Y12 inhibitor 668 (3.4) 354 (3.2) 202 (4.1) 295 (4.3) 1519 (3.6)

Only ASA 288 (1.5) 3105 (28.2) 151 (3.1) 1860 (26.7) 5404 (12.3)

Only OAC 21 (0.1) 312 (2.8) 15 (0.3) 339 (4.9) 687 (1.6)

OAC + DAPT 925 (4.7) 241 (2.2) 473 (9.6) 165 (2.4) 1804 (4.2)

OAC + P2Y12 inhibitor 58 (0.3) 40 (0.4) 28 (0.6) 58 (0.8) 184 (0.4)

OAC + ASA 43 (0.2) 520 (4.7)) 32 (0.7) 529 (7.6) 1124 (2.6)

No antiplatelet or OAC 327 (1.7) 1329 (12.1) 140 (2.9) 1103 (15.9) 2899 (6.8)

Statins 19 168 (96.6) 9224 (83.8) 4574 (93.0) 5262 (75.7) 38 228 (89.5)

Beta-blockers 16 763 (84.5) 8529 (77.5) 4238 (86.2) 5456 (78.6) 34 986 (81.9)

ACE inhibitors 7977 (40.3) 3478 (31.7) 2027 (41.2) 2497 (36.0) 15 988 (37.4)

ARB 4822 (24.3) 2945 (26.8) 1597 (32.5) 2072 (29.8) 11 346 (26.8)

Numbers in parentheses are percentages of total number of patients in the group. SD denotes standard derivation, DAPT dual antiplatelet therapy, AMI Acutemyocardial infaction, ASA Acetylsalicylic acid, OAC Oral anticoagulants, ACE Angiotensin-converting enzyme, ARB Angiotensin II receptor blocker

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Table 2 Secondary preventive drugs at discharge from hospital for index AMI and 12˗18 months later; patients <85 years

Secondary preventive drugsat discharge for index AMI

Secondary preventive drugs12–18 months after index AMI

(n = 42 707) (n = 28 767)

n (%) Mean dose (mg) n (%) Mean dose (mg) n (%) switched to another drugwithin same drug class inpost-AMI period

n (%) changed dose of actualdrug in post-AMI period

Statins 38 228 (89.5) 24 062 (83.6)

Simvastatin 23 528 (55.1) 37.2 12 478 (43.4) 38.4 2571 (15.7) 1415 (8.7)

Atorvastatin 17 084 (40.0) 56.9 10 913 (37.9) 52.1 592 (6) 1755 (17.8)

Rosuvastatin 225 (0.5) 17.7 367 (1.3) 19.6 10 (9.6) 13 (12.5)

Pravastatin 1158 (2.7) 33.5 651 (2.3) 33.5 120 (20.9) 39 (6.8)

ACEI/ARBa 25 445 (59.6) 16 274 (56.6)

Losartan 3658 (8.6) 66.6 2049 (7.1) 66.5 153 (6.9) 238 (10.8)

Candersartan 4157 (9.7) 13.1 2778 (9.7) 13.5 145 (5.4) 467 (17.4)

Valsartan 1503 (3.5) 124.9 865 (3.0) 125.2 68 (7.2) 127 (13.4)

Irbesartan 1530 (3.6) 235.6 770 (2.7) 237.3 72 (7.8) 61 (6.6)

Enalapril 2951 (6.9) 11.8 1657 (5.8) 11.9 170 (8.9) 324 (16.9)

Ramipril 11 492 (26.9) 3.5 6999 (24.3) 4.5 733 (8.8) 2156 (25.8)

Lisinopril 1753 (4.1) 11.3 949 (3.3) 11.3 121 (10.3) 207 (17.5)

Beta-blockers 34 986 (81.9) 22 061 (76.7)

Metoprolol 30 874 (72.3) 60.6 18 920 (65.8) 62.3 702 (3.2) 4452 (20.3)

Atenolol 1381 (3.2) 52.4 457 (1.6) 51.0 117 (21.6) 54 (10)

Propranolol 305 (0.7) 66.2 82 (0.3) 80.4 26 (26.3) 6 (6.1)

Sotalol 358 (0.8) 80.3 138 (0.5) 75.9 49 (33.3) 14 (9.5)

Bisoprolol 2477 (5.8) 4.1 1856 (6.5) 4.4 64 (4) 310 (19.3)

Carvedilol 1298 (3.0) 15.8 813 (2.8) 15.6 73 (9.1) 123 (15.3)

Numbers in parentheses are percentages of total number of patients in the groupACEI Angiotensin-converting enzyme inhibitor, AMI Aciute myocardial infraction, ARB Angiotensin II receptor blockerasome patients were prescribed both ACEI and ARB

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Although long-term compliance was reasonably good,patients who did not start treatment shortly after dis-charge had a low probability of starting treatment later[12]. In a more recent Swedish study, both initiationand long-term adherence to secondary preventive drugtherapy was higher and similar to our findings: 82 %of AMI patients were still on aspirin 12 months postAMI, 73 % on statins and 80 % on beta-blockers [18].

A high degree of initiation of secondary preventivedrug therapy was also observed in a recent study fromthe United States [13]. However, when patients weredivided into risk groups based on the Global Registryof Acute Coronary Event (GRACE) risk score at hospitaldischarge, high-risk patients had a lower likelihood of re-ceiving all appropriate therapies at discharge comparedwith low-risk patients.

Fig. 2 Adherence to secondary preventive drugs over time in AMI patients ≤75 years with or without PCI. Norway 2009–2013. Abbreviations: ASA,acetylsalicylic acid; ACEI, angiotensin-converting enzyme inhibitor; AMI, acute myocardial infarction; ARB, angiotensin II receptor blocker; PCI,percutaneous coronary intervention

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Our data may indicate that if secondary preventivedrug therapy after AMI is not prescribed at hospitaldischarge, the likelihood of receiving such treatment islimited. Thus, initiation of guideline-recommended second-ary preventive drug therapy after AMI seems to depend onthe hospital physicians, in accordance with the previous ob-servations from Denmark [12]. The present study furtherdemonstrates that only minor dose adjustments for drugs

prescribed at discharge were performed by the primary carephysicians during follow-up. Thus, Norwegian primary carephysicians seemed reluctant to changing already prescribedsecondary preventive drug therapies after AMI.This finding further underscores the importance of drug

prescription prior to discharge of AMI patients from hospi-tals. Not only should AMI patients be prescribed guideline-recommended secondary preventive drugs, but the hospital

Fig. 3 Adherence to secondary preventive drugs over time in AMI patients 76–84 years with and without PCI. Norway 2009–2013. Abbreviations:ASA, acetylsalicylic acid; ACEI, angiotensin-converting enzyme inhibitor; AMI, acute myocardial infarction; ARB, angiotensin II receptor blocker; PCI,percutaneous coronary intervention

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physicians could also advice on further up-titration and thetarget doses of the prescribed drugs in the discharge sum-mary sent to the patient’s general practitioner. It is alsoimportant that the general practitioners are updatedon current guidelines and take the responsibility foroptimizing secondary preventive treatment after AMI.Interestingly, patients not undergoing PCI were lesslikely to receive guideline-recommended secondarypreventive drugs compared with patients undergoingPCI. For example, a 10–20 % higher use of statins and

beta-blockers was seen in PCI patients vs. patients notundergoing PCI. Furthermore, a larger portion of pa-tients not undergoing PCI was discharged without aP2Y12 inhibitor (48 % and 55 %, respectively, in pa-tients ≤75 or 76–84 years) compared with PCI patients(4 % and 7 %). The reasons for this undertreatment ofnon-PCI patients are not known. We might speculatethat a higher degree of comorbidities might be presentin these patients, making the physicians more selectivein their prescription of secondary preventive drugs.

Fig. 4 Adherence to treatment with different P2Y12 inhibitors in AMI patients <85 years with and without PCI. Norway 2009–2013. Abbreviations:AMI, acute myocardial infarction; PCI, percutaneous coronary intervention

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The mean doses of both ACEI, ARB and beta-blockersin our study were lower than the target doses in ran-domized trials studying the efficacy and safety of thesedrugs. The reasons for the choice of these lower doses,or the lack of up-titration of doses after hospital dis-charge, are unknown. These drugs are used for a varietyof indications, and since we have limited data on weight,blood pressure, heart rate, ejection fraction, comorbidi-ties and on the specific indications for the various drugs(e.g. for ACEI/ARB), we find it difficult to draw any firmconclusions regarding target doses and whether thedoses used in our study were too low or not. With re-spect to statin treatment, it should be noted that duringmost of our study period, no specific statin dose wasrecommended and statins were prescribed mainly ac-cording to LDL-cholesterol levels.We observed a generally short duration of P2Y12 in-

hibitor treatment for patients not undergoing PCI(Fig. 4), with a significant proportion of patients treatedfor only three months as also observed in a recent studyfrom Sweden [19]. One possible reason for the longertreatment duration after PCI may be that P2Y12 inhib-ition is regarded particularly important after stent im-plantation to avoid stent thrombosis. However, ESCguidelines recommend P2Y12 inhibition for 12 months inall ACS patients [3–6].A large proportion of patients discontinued P2Y12 in-

hibitor after nine months; mainly patients on clopido-grel treatment. One likely explanation to this findingwas the nine months’ limited reimbursement of clopi-dogrel in Norway until September 2011 [20]. Prasugreland ticagrelor have not had such reimbursement limita-tions. This finding demonstrates the influence thehealth authorities have on medical treatment by deter-mining the prescription rules for reimbursements ofvarious drugs.

LimitationsOur data set provides a unique possibility to examineadherence to antiplatelet therapy, statins, beta-blockersand ACEI/ARB. It includes nationwide data from all pa-tients hospitalized in Norway for AMI in 2009–2013,allowing analyses of a complete and unselected cohort ofpatients, and also allowing differentiation between youngerand older patients and between patients undergoing PCI ornot. This reduces potential problems arising from selectionbias due to inclusion of selected hospitals, regions, or healthcare insurance systems. Furthermore, by restricting theinclusion to patients below 85 years of age, this studyfocuses on patients who normally would be considered tobe treated according to guidelines. However, this register-based analysis also has certain limitations. As our analysisrelied on ICD-10 codes, the possibility of coding errors can-not be ruled out, although the primary diagnoses of AMI

previously have been shown to have high sensitivity andspecificity [21]. A further subclassification of patients intothose presenting with and without persistent ST-segmentelevation on the electrocardiogram could not be per-formed due to non-validated ICD-10 coding specifica-tion at this level.Further, due the study aim describing secondary

drug adherence in a nationwide patient population,patients were included based on their first AMI duringthe observational period, i.e. not necessarily their firsttime AMI. Thus, the patient population changed dur-ing the inclusion period. While patients included earlyin the inclusion period may have had a recent historyof AMI, patients included towards the end of thestudy period had to be event-free for a longer time.Following from this study design, the yearly numbersof included AMIs in our study decreased during theobservational period (Additional file 1, Table 1). Fur-thermore, how a recent prior AMI episode wouldaffect selection for invasive treatment and secondaryprevention drugs is difficult to predict, but it cannotbe excluded that these patients would receive a higherattention, and thus a higher likelihood of receivingguideline-recommended treatment.The registry data were collected for administrative pur-

poses and we did not have any information on smokingpatterns, weight, blood pressure, laboratory data or socio-economic status. Furthermore, the Norwegian PatientRegister has only had nationwide coverage since 2009 andmedical history from previous hospitalizations was notavailable.

ConclusionsThis nationwide observational study, including all pa-tients in Norway below 85 years of age being alive 30days after AMI during the years 2009 to 2013, showed agenerally high long-term adherence to antiplatelet ther-apy, as well as treatment with statins, beta-blockers andACEI/ARB. To a large extent, PCI patients receivedguideline-recommended treatment with secondary pre-ventive drugs. Patients not undergoing PCI were lesslikely to be discharged with the recommended drugs.The shift of responsibility for prescribing drug treat-ment from hospital to primary health care did not toany major extent alter the already prescribed treat-ments. Thus, the majority of AMI patients remained onthe secondary preventive treatment originally pre-scribed, further underlining the importance of prescrib-ing guideline-recommended drug treatment at hospitaldischarge, and preferably including specialist guidanceon future target doses in the discharge summary. Thepresent study also indicates a need for more careful at-tention to secondary preventive drug therapy in AMIpatients not undergoing PCI.

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AbbreviationsACEI, angiotensin-converting enzyme inhibitor; AMI, acute myocardial infarction;ARB, angiotensin II receptor blocker; ASA, acetylsalicylic acid; DAPT, dual antiplate-let therapy; ICD-10-CM, International Classification of Diseases, 10th revision, Clin-ical Modification; OAC, oral anticoagulant; PCI, percutaneous coronaryintervention.

Additional file

Additional file 1: Table S1. Proportion of AMI patients undergoing PCIbetween 2009 and November 2013. Table S2. Adherence to P2Y12inhibitors after index AMI. (DOCX 23 kb)

FundingThis work was supported by AstraZeneca. Project management was providedby AstraZeneca. The statistical analysis was agreed upon by the study steeringcommittee, and data analysis was performed by the study database owner incollaboration with AstraZeneca. AstraZeneca took part as members of the studysteering committee in the interpretation of the data and the drafting of themanuscript.

Availability of data and materialsThe dataset supporting the conclusions of this article is still subject to furtheranalyses, and will continue to be held and managed by the NorwegianUniversity of Science and Technology, Trondheim, Norway. Relevantanonymized patient level data are available from the authors on request.

Authors’ contributionsS. Halvorsen, J. Jortveit, P. Hasvold, M. Thuresson, and E. Øie, participatedequally in the study conception, design, and statistical analysis planning. M.Thuresson was responsible for the statistical analyses and S. Halvorsen forthe manuscript draft and finalization. All authors had access to study data,and had authority over manuscript preparation, approval of the final version,and the decision to submit for publication.

Competing interestsAll authors have completed the Unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (http://www.icmje.org/coi_disclosure.pdf)(available on request from the corresponding author). SH declare support fromAstraZeneca for the submitted work, and personal fees from AstraZeneca, Pfizer,BMS, Eli Lilly, Sanofi, Novartis and MSD outside of the submitted work. JJ declaresupport from AstraZeneca for the submitted work, and personal fees fromAstraZeneca, Pfizer and Sanofi outside of the submitted work. PH is employed byAstraZeneca. MT is employed by an independent statistical consultant company,Statisticon, for which AstraZeneca is a client. EØ declare support from AstraZeneca for the submitted work, and personal fees from AstraZeneca, Pfizer, BMS,Takeda, Novartis, Sanofi and MSD outside of the submitted work.

Ethics approvalThe study pyrotocol was approved by the the Regional Ethics Committee ofNorth Norway (Reference number 2014/70/REK nord). Registration of datainto the National registries in this study, does not require patients’ consent.

DisclaimersThis study has used data from the Norwegian Cause of Death Registry. Theinterpretation and reporting of these data is the sole responsibility of theauthors, and no endorsement by the Norwegian Cause of Death Registry isintended, nor it should be inferred.

Author details1Department of Cardiology, Oslo University Hospital Ulleval and University ofOslo, Postboks 4956, Nydalen 0424, Oslo, Norway. 2Department ofCardiology, Sørlandet Hospital, Arendal, Norway. 3AstraZeneca NordicBaltic,Södertälje, Sweden. 4Statisticon, Uppsala, Sweden. 5Department of InternalMedicine, Diakonhjemmet Hospital, and Center for Heart Failure Research,University of Oslo, Oslo, Norway.

Received: 18 January 2016 Accepted: 14 May 2016

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